IIRC the majority, if not all, examples I have seen posted on various websites have been Dearborn and SJ cars. I'd take no exception to Metuchen doing something different. SJ seems to have been famous (or infamous if you prefer!), for this.
My point in posting was the blanket statement that has accompanied every reference post alludes to the fact that if the additional reinforcement isn't there, it's ain't real! Bottom line, it isn't a 100% accurate reference point to look at, uncommon or not!
BTW, a friend owns an 01/66 scheduled date Metuchen GT coupe. I don't recall ever seeing the reinforcement on his. I will check to confirm though and post the results. It is quit possibly a Metuchen thing.
p.s. If I didn't mention it, mine had a schedule date of 10/65.